Attachment for micrometer calipers



Filed March '7, 19 12 JOHN J. BRADY INVENTOR I T, 2? v.

ATTORNEY Patented May 4, 1943 ATTACHMENT FOR MICROMETER CALIPERS .lohnlBrady, Providence, R. 1.

Application March 7, 1942, Serial No. 433,719

2 Claims.

This invention relates to attachment for micrometer calipers, and more particularlyto means of this character adapted for use in connection with the measurement of the effective cutting edges of staggered toothed side milling cutters and the like, wherein the cutting edges of alternate teeth are-offset oppositelyfrom each-other.

One object of the invention is to provide a simple form of attachment for micrometer calipers adapted for ready application to or removal from a micrometer of the conventional type, and which is capable of providing means for indicating quickly and exactly the overall width of oppositely offset cutting teeth.

Another object of the invention is the-provision of an attachment of this character comprising a member of substantially rigid character having a plane contact face adapted to be positioned in fixed relation with the anvil face of a micrometer and means carried by the member for ready attachment to and removal from a portion of the micrometer structure in such a manner as to locate the plane face of the member at right angles with the axis of movement of the spindle and in definitely fixed relation with the face of the anvil.

Other objects of the invention relate to various improved details of COIlStl'llCtiOllfll'Id novel arrangements of the parts as will be more fully set forth in the detailed description to follow.

Referring to the drawing:

Fig. 1 is a perspective view of a micrometer caliper structure of a conventional type showing the attachment applied thereto and illustrating the same in connection with the measuring'of the cutting face of'a tooth relative to the plane defined by the cutting faces of oppositely directed teeth of a staggered toothed side milling cutter of a type in common use,

Fig. 2 is an end elevational view of the attachment, showing the same as applied to the micrometer structure, and,

Fig. 3 is a side elevational view of the attachment, taken substantially along the line 33 of Fig. 2, showing the location of the cutting edges of the teeth of a side milling cutter with respect to the contact face of the attachment and the micrometer spindle when located in operative relation with the attachment for measuring a cutting tooth.

In the form of the invention shown and described herein, l designates a micrometer caliper structure of a conventional character which comprises a U-shaped frame portion 2, having a barrel 3 on which is mounted a thimble 4 provided with a knurled head 5. A spindle 6 is mounted within the barrel 3 for longitudinal movement in the direction of its axis upon rotation of the thimble 4. An anvil I, carried by the frame 2, is suitably positioned for engagement by the end of the spindle 6, and may be capable of adjustment in a direction toward and from the spindle to secure and maintain proper correlation of the spindle with the scale of measurement of the micrometer, as is well-known in the art.

An indicating scale'8 is formed on the barrel 3, comprising main division lines 9, which may be graduated to read directly in hundred-thousandths of an inch the travel of the spindle relative to the contact face of the anvil I through correspondence of the end of the thimble 4 with the division lines 9. A vernier scale l0 carried by the thimble end H, as shown, is positioned to cooperate with the scale'8 for indicating fractional parts of himdred-thousandths of an inch upon micrometers of the type specified.

The attachment proper, which is indicated generally 'by the reference character I l, comprises an anvil member I5, of a character and thickness rendering it substantially rigid under such pressure as it is likely to be subjected when in use for measuring devices of the character indicated, and which is, provided with a plane contact face E6 of substantial area so formed as to be positioned in a fixed and-predeterm ned relation with the contact face of the anvil I when in operative position on the micrometer which relation preferably coincides with a specified hundredthousandths line 9 of the scale 8, in order that direct readings maybe made without resort to computation.

Means is provided for securing the anvil member E5 to the micrometer l or a suitable portion of the frame thereof, which may comprise a sleeve l8 formed integral with or firmly and accurately secured to the anvil member l5, preferably in such a manner that the axis of the sleeve [8 is perpendicular to the contact face It of the member I 5. As shown, the circular extent of the sleeve I8 is somewhat in excess of degrees, and the free edges 19 of the sleeve are cut away slightly at points 20 adjacent to the member 15, in order that the free edges I9 may be forced over and engage releasably the sides of the micrometer frame adjacent to the anvil 1 in such a manner as to clamp the member I5 firmly in position on the micrometer frame when in use.

Staggered toothed side milling cutters, in connection with which the present attachment is particularly adapted for use, may be of a form as shown herein and indicated generally by the reference character 22, which comprises a plurality of cutting teeth 23 and 24, of which the teeth 23 have side cutting surfaces 25 projecting outwardly from one side of the plane of the cutter, while the cutting teeth 24 have side cutting surfaces 26 projecting outwardly from the opposite side of the general plane of the cutter.

In order to grind properly the oppositely directed cutting edges of alternately arranged cutting teeth in a cutter of this character it is necessary to measure accurately the position of each cutting edge with reference to cutting edges of at least the two teeth next adjacent thereto in order to determine accurately and maintain constantly uniform the fixed transverse extent of the cutting field or the plane of cut on each side of the cutter throughout the entire circular extent of the cutter itself. This requires that measurement be made from the side cutting edge of each tooth to the plane of the cutting edges of the oppositely directed offset teeth, and this may be determined by measuring from the cutting edge of each tooth to the plane determined by the cutting edges of the two next adjacent teeth, the cutting edges of which are oppositely directed with respect to the cutting edge of the tooth being measured.

In other words, referring to the cutter shown herein, the cutting edges 25 of the teeth 23 lie in a common plane from which the cutting edges 26 of the teeth 24 should project equal or substantially equal distances in order that the cutting edges 26 of the teeth 24 may lie in a common plane parallel with the plane of the cutting edges 25. In order to maintain the cutting edges of the teeth in the relation above described it is necessary that the cutting edges of the teeth of each set be groundaccurately with reference to the plane of the cutting edges of the teeth of the oppositely directed set. In practice, this cannot be done quickly and accurately by measuring the distance between the cutting edges of adjacent oppositely directed teeth, but requires that measurement of the cutting edge of each tooth be made with reference to the plane of the cutting edges of the oppositely directed teeth, which plane may be determined substantially by reference to the cutting edges of two or more of the oppositely directed teeth located adjacent to the particular tooth which is to be ground.

In order to accomplish this measurement a plane base of substantial surface extent, the area of which depends somewhat upon the diameter of the cutter, is required to serve as a contact face for the cutting edges of the two or more op positely directed teeth located upon opposite sides of the tooth to be measured. By means of the attachment shown, the cutting edges of the teeth upon opposite sides of that to be engaged by the spindle are positioned upon the contact face l6 of the member [5 and when the spindle 6 is brought into contact with the cutting edge of the intermediate tooth the direct reading of the scale less the thickness of the plate member shows the overall thickness of the cutter which is required and the amount of grinding necessary to bring the cutting edge of each tooth into correspondence with the desired plane of cut.

I claim:

1. An attachment for micrometer calipers adapted for use in measuring any one of plural unidirectional surfaces of a member with reference to a plane determined by a series of oppositely directed surfaces which comprises, a substantially rigid anvil member provided with a plane contact face of substantial extent for engaging two or more of the series of oppositely directed surfaces simultaneously and serving to support the member in a plane substantially coincident with the plane of the series of oppositely directed surfaces, and means comprising a split sleeve having oppositely positioned straight edges engageable with opposite sides of the frame portion of the micrometer calipers for securing said anvil member thereto in such a manner as to maintain the plane contact face portion of the anvil member substantially perpendicular to the longitudinal axis of the micrometer spindle while engaged at two or more points by oppositely directed contact surfaces of the member to be measured. 1

2. An attachment for micrometer calipers havinga jaw supported anvil and a spindle member movable toward and from the jaw supported anvil along a fixed path, comprising an auxiliary anvil member provided with a plane contact face vof materially greater superficial extent than the contact face of the jaw supported anvil, and a split sleeve member carried by said auxiliary anvil member and provided with oppositely positioned free edge portions engageable with opposite sides of the anvil supporting jaw substangaged by an article to be measured at two or more points the locus of which may be offset from the axis of movement of the spindle member.

JOHN J. BRADY. 

